addi $s0, $0, 1000 # n = 1000
addi $s1, $0, 0    # s = 0
addi $s2, $0, 1    # i = 1
FOR:
slt $t0, $s2, $s0  # $t0 = i < n?
bne $t0, $0, END   # if !(i < n) goto END
add $s1, $s1, $s2  # s = s + i
addi $s2, $s2, 1   # i = i + 1
j FOR
END:
addi $s1, $0, 0    # s = 0